Index / Units
Dog and Cat Years
An animal's age in human-equivalent years, worked out three ways: the size-based table vets use, the 2020 epigenetic clock, and the seven-times rule, which is here so you can see how far off it is.
The animal
Size matters more than anything else here: a
great dane ages roughly twice as fast as a chihuahua.
In human years
--
Life stage
--
Of a typical lifespan
--
The three methods, side by side
The other direction
your age, in theirsYear by year
Where each of these numbers comes from
The size table. A dog's first year counts as about 15 human
years and the second adds about 9, putting a two-year-old dog at 24.
After that each year adds 4 for a small dog, 5 for a medium one, 6 for a
large one and 7 for a giant breed. That is the table veterinary
associations publish, and the size split is the important part: a
chihuahua and a great dane are the same age at two and nowhere near it
at ten.
The cat table works the same way and does not depend on size: 15 for the first year, 9 for the second, and 4 for every year after.
The epigenetic clock is 16 × ln(age) + 31, from Wang and colleagues in 2020. They compared DNA methylation in dogs and humans and fitted that curve. It is worth knowing what it is not: it was fitted on 104 Labrador retrievers, so it carries no size term at all, and being a logarithm it has nothing to say about a very young puppy: the curve crosses zero at e−31/16 years, about 1.7 months, and goes to negative infinity at an age of zero. Below that crossing this page shows nothing rather than a negative number.
The seven-times rule is folklore, and it is printed here to be looked at rather than used. It seems to come from noticing that people lived to about 70 and dogs to about 10 and dividing. It is roughly right in the middle of a medium dog's life and badly wrong at both ends: it makes a one-year-old dog seven, when a one-year-old dog can already reproduce.
Typical lifespans used for the percentage are 14 years for a small dog, 13 for a medium, 11 for a large, 8 for a giant breed, and 15 for a cat. These are middles of wide ranges, and an individual animal is not a distribution.
The life stages are this page's own boundaries, drawn on the human-equivalent number: under 20 is young, 20 to 44 is adult, 45 to 64 is mature, and 65 and over is senior. Vets stage animals on physical examination, not on arithmetic.
None of this is veterinary advice, and no formula here knows anything about the animal in front of you.
The cat table works the same way and does not depend on size: 15 for the first year, 9 for the second, and 4 for every year after.
The epigenetic clock is 16 × ln(age) + 31, from Wang and colleagues in 2020. They compared DNA methylation in dogs and humans and fitted that curve. It is worth knowing what it is not: it was fitted on 104 Labrador retrievers, so it carries no size term at all, and being a logarithm it has nothing to say about a very young puppy: the curve crosses zero at e−31/16 years, about 1.7 months, and goes to negative infinity at an age of zero. Below that crossing this page shows nothing rather than a negative number.
The seven-times rule is folklore, and it is printed here to be looked at rather than used. It seems to come from noticing that people lived to about 70 and dogs to about 10 and dividing. It is roughly right in the middle of a medium dog's life and badly wrong at both ends: it makes a one-year-old dog seven, when a one-year-old dog can already reproduce.
Typical lifespans used for the percentage are 14 years for a small dog, 13 for a medium, 11 for a large, 8 for a giant breed, and 15 for a cat. These are middles of wide ranges, and an individual animal is not a distribution.
The life stages are this page's own boundaries, drawn on the human-equivalent number: under 20 is young, 20 to 44 is adult, 45 to 64 is mature, and 65 and over is senior. Vets stage animals on physical examination, not on arithmetic.
None of this is veterinary advice, and no formula here knows anything about the animal in front of you.